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* mm: flush dcache before writing into page to avoid aliasanfei zhou2010-02-021-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The cache alias problem will happen if the changes of user shared mapping is not flushed before copying, then user and kernel mapping may be mapped into two different cache line, it is impossible to guarantee the coherence after iov_iter_copy_from_user_atomic. So the right steps should be: flush_dcache_page(page); kmap_atomic(page); write to page; kunmap_atomic(page); flush_dcache_page(page); More precisely, we might create two new APIs flush_dcache_user_page and flush_dcache_kern_page to replace the two flush_dcache_page accordingly. Here is a snippet tested on omap2430 with VIPT cache, and I think it is not ARM-specific: int val = 0x11111111; fd = open("abc", O_RDWR); addr = mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0); *(addr+0) = 0x44444444; tmp = *(addr+0); *(addr+1) = 0x77777777; write(fd, &val, sizeof(int)); close(fd); The results are not always 0x11111111 0x77777777 at the beginning as expected. Sometimes we see 0x44444444 0x77777777. Signed-off-by: Anfei <anfei.zhou@gmail.com> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Miklos Szeredi <miklos@szeredi.hu> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: <linux-arch@vger.kernel.org> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fuse: fix kunmap in fuse_ioctl_copy_userJens Axboe2009-11-041-1/+1
| | | | | | | | | | | Looks like another victim of the confusing kmap() vs kmap_atomic() API differences. Reported-by: Todor Gyumyushev <yodor1@gmail.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: stable@kernel.org
* fuse: prevent fuse_put_request on invalid pointerAnand V. Avati2009-11-041-1/+2
| | | | | | | | | | fuse_direct_io() has a loop where requests are allocated in each iteration. if allocation fails, the loop is broken out and follows into an unconditional fuse_put_request() on that invalid pointer. Signed-off-by: Anand V. Avati <avati@gluster.com> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Cc: stable@kernel.org
* const: mark struct vm_struct_operationsAlexey Dobriyan2009-09-271-1/+1
| | | | | | | | | | | * mark struct vm_area_struct::vm_ops as const * mark vm_ops in AGP code But leave TTM code alone, something is fishy there with global vm_ops being used. Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fuse: fix bad return value in fuse_file_poll()Miklos Szeredi2009-06-301-1/+1
| | | | | | | | Fix fuse_file_poll() which returned a -errno value instead of a poll mask. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> CC: stable@kernel.org
* fuse: export symbols to be used by CUSETejun Heo2009-04-281-7/+13
| | | | | | | | | | | | | | | | | | | | | | | | Export the following symbols for CUSE. fuse_conn_put() fuse_conn_get() fuse_conn_kill() fuse_send_init() fuse_do_open() fuse_sync_release() fuse_direct_io() fuse_do_ioctl() fuse_file_poll() fuse_request_alloc() fuse_get_req() fuse_put_request() fuse_request_send() fuse_abort_conn() fuse_dev_release() fuse_dev_operations Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: don't use inode in fuse_file_pollMiklos Szeredi2009-04-281-3/+2
| | | | | | | | | | Use ff->fc and ff->nodeid instead of file->f_dentry->d_inode in the fuse_file_poll() implementation. This prepares this function for use by CUSE, where the inode is not owned by a fuse filesystem. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: don't use inode in fuse_do_ioctl() helperMiklos Szeredi2009-04-281-14/+21
| | | | | | | | | | Create a helper for sending an IOCTL request that doesn't use a struct inode. This prepares this function for use by CUSE, where the inode is not owned by a fuse filesystem. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: don't use inode in fuse_sync_release()Miklos Szeredi2009-04-281-20/+29
| | | | | | | | | Make fuse_sync_release() a generic helper function that doesn't need a struct inode pointer. This makes it suitable for use by CUSE. Change return value of fuse_release_common() from int to void. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: create fuse_do_open() helper for CUSEMiklos Szeredi2009-04-281-25/+40
| | | | | | | Create a helper for sending an OPEN request that doesn't need a struct inode pointer. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: clean up args in fuse_finish_open() and fuse_release_fill()Miklos Szeredi2009-04-281-13/+15
| | | | | | | | | | | Move setting ff->fh, ff->nodeid and file->private_data outside fuse_finish_open(). Add ->open_flags member to struct fuse_file. This simplifies the argument passing to fuse_finish_open() and fuse_release_fill(), and paves the way for creating an open helper that doesn't need an inode pointer. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: don't use inode in helpers called by fuse_direct_io()Miklos Szeredi2009-04-281-32/+30
| | | | | | | | | Use ff->fc and ff->nodeid instead of passing down the inode. This prepares this function for use by CUSE, where the inode is not owned by a fuse filesystem. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: add members to struct fuse_fileMiklos Szeredi2009-04-281-0/+2
| | | | | | | | Add new members ->fc and ->nodeid to struct fuse_file. This will aid in converting functions for use by CUSE, where the inode is not owned by a fuse filesystem. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: prepare fuse_direct_io() for CUSEMiklos Szeredi2009-04-281-10/+23
| | | | | | | | | Move code operating on the inode out from fuse_direct_io(). This prepares this function for use by CUSE, where the inode is not owned by a fuse filesystem. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: clean up fuse_write_fill()Miklos Szeredi2009-04-281-9/+8
| | | | | | | | | | Move out code from fuse_write_fill() which is not common to all callers. Remove two function arguments which become unnecessary. Also remove unnecessary memset(), the request is already initialized to zero. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: use struct path in release structureMiklos Szeredi2009-04-281-5/+4
| | | | | | | Use struct path instead of separate dentry and vfsmount in req->misc.release. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: misc cleanupsTejun Heo2009-04-281-37/+44
| | | | | | | | | | | | * fuse_file_alloc() was structured in weird way. The success path was split between else block and code following the block. Restructure the code such that it's easier to read and modify. * Unindent success path of fuse_release_common() to ease future changes. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: fix "direct_io" private mmapMiklos Szeredi2009-04-091-0/+2
| | | | | | | | | MAP_PRIVATE mmap could return stale data from the cache for "direct_io" files. Fix this by flushing the cache on mmap. Found with a slightly modified fsx-linux. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: fix argument type in fuse_get_user_pages()Miklos Szeredi2009-04-091-3/+3
| | | | | | | | | | | | Fix the following warning: fs/fuse/file.c: In function 'fuse_direct_io': fs/fuse/file.c:1002: warning: passing argument 3 of 'fuse_get_user_pages' from incompatible pointer type This was introduced by commit f4975c67 "fuse: allow kernel to access "direct_io" files". Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: allow private mappings of "direct_io" filesMiklos Szeredi2009-04-021-1/+11
| | | | | | | | | | | | Allow MAP_PRIVATE mmaps of "direct_io" files. This is necessary for execute support. MAP_SHARED mappings require some sort of coherency between the underlying file and the mapping. With "direct_io" it is difficult to provide this, so for the moment just disallow shared (read-write and read-only) mappings altogether. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: allow kernel to access "direct_io" filesMiklos Szeredi2009-04-021-12/+30
| | | | | | | | | | | Allow the kernel read and write on "direct_io" files. This is necessary for nfs export and execute support. The implementation is simple: if an access from the kernel is detected, don't perform get_user_pages(), just use the kernel address provided by the requester to copy from/to the userspace filesystem. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* mm: page_mkwrite change prototype to match faultNick Piggin2009-04-011-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | Change the page_mkwrite prototype to take a struct vm_fault, and return VM_FAULT_xxx flags. There should be no functional change. This makes it possible to return much more detailed error information to the VM (and also can provide more information eg. virtual_address to the driver, which might be important in some special cases). This is required for a subsequent fix. And will also make it easier to merge page_mkwrite() with fault() in future. Signed-off-by: Nick Piggin <npiggin@suse.de> Cc: Chris Mason <chris.mason@oracle.com> Cc: Trond Myklebust <trond.myklebust@fys.uio.no> Cc: Miklos Szeredi <miklos@szeredi.hu> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Joel Becker <joel.becker@oracle.com> Cc: Artem Bityutskiy <dedekind@infradead.org> Cc: Felix Blyakher <felixb@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fuse: fix fuse_file_lseek returning with lock heldDan Carpenter2009-03-301-1/+2
| | | | | | | | | This bug was found with smatch (http://repo.or.cz/w/smatch.git/). If we return directly the inode->i_mutex lock doesn't get released. Signed-off-by: Dan Carpenter <error27@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> CC: stable@kernel.org
* fuse: fix NULL deref in fuse_file_alloc()Dan Carpenter2009-01-261-1/+1
| | | | | | | | ff is set to NULL and then dereferenced on line 65. Compile tested only. Signed-off-by: Dan Carpenter <error27@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> CC: stable@kernel.org
* Merge branch 'for-linus' of ↵Linus Torvalds2009-01-061-19/+438
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse: fuse: clean up annotations of fc->lock fuse: fix sparse warning in ioctl fuse: update interface version fuse: add fuse_conn->release() fuse: separate out fuse_conn_init() from new_conn() fuse: add fuse_ prefix to several functions fuse: implement poll support fuse: implement unsolicited notification fuse: add file kernel handle fuse: implement ioctl support fuse: don't let fuse_req->end() put the base reference fuse: move FUSE_MINOR to miscdevice.h fuse: style fixes
| * fuse: clean up annotations of fc->lockHarvey Harrison2008-12-021-0/+4
| | | | | | | | | | | | | | | | Makes the existing annotations match the more common one per line style and adds a few missing annotations. Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
| * fuse: fix sparse warning in ioctlMiklos Szeredi2008-12-021-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | Fix sparse warning: CHECK fs/fuse/file.c fs/fuse/file.c:1615:17: warning: incorrect type in assignment (different address spaces) fs/fuse/file.c:1615:17: expected void [noderef] <asn:1>*iov_base fs/fuse/file.c:1615:17: got void *<noident> This was introduced by "fuse: implement ioctl support". Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
| * fuse: add fuse_ prefix to several functionsTejun Heo2008-11-261-14/+14
| | | | | | | | | | | | | | | | | | | | Add fuse_ prefix to request_send*() and get_root_inode() as some of those functions will be exported for CUSE. With or without CUSE export, having the function names scoped is a good idea for debuggability. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
| * fuse: implement poll supportTejun Heo2008-11-261-0/+132
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Implement poll support. Polled files are indexed using kh in a RB tree rooted at fuse_conn->polled_files. Client should send FUSE_NOTIFY_POLL notification once after processing FUSE_POLL which has FUSE_POLL_SCHEDULE_NOTIFY set. Sending notification unconditionally after the latest poll or everytime file content might have changed is inefficient but won't cause malfunction. fuse_file_poll() can sleep and requires patches from the following thread which allows f_op->poll() to sleep. http://thread.gmane.org/gmane.linux.kernel/726176 Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
| * fuse: add file kernel handleTejun Heo2008-11-261-2/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | The file handle, fuse_file->fh, is opaque value supplied by userland FUSE server and uniqueness is not guaranteed. Add file kernel handle, fuse_file->kh, which is allocated by the kernel on file allocation and guaranteed to be unique. This will be used by poll to match notification to the respective file but can be used for other purposes where unique file handle is necessary. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
| * fuse: implement ioctl supportTejun Heo2008-11-261-0/+280
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Generic ioctl support is tricky to implement because only the ioctl implementation itself knows which memory regions need to be read and/or written. To support this, fuse client can request retry of ioctl specifying memory regions to read and write. Deep copying (nested pointers) can be implemented by retrying multiple times resolving one depth of dereference at a time. For security and cleanliness considerations, ioctl implementation has restricted mode where the kernel determines data transfer directions and sizes using the _IOC_*() macros on the ioctl command. In this mode, retry is not allowed. For all FUSE servers, restricted mode is enforced. Unrestricted ioctl will be used by CUSE. Plese read the comment on top of fs/fuse/file.c::fuse_file_do_ioctl() for more information. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
| * fuse: don't let fuse_req->end() put the base referenceTejun Heo2008-11-261-3/+2
| | | | | | | | | | | | | | | | | | fuse_req->end() was supposed to be put the base reference but there's no reason why it should. It only makes things more complex. Move it out of ->end() and make it the responsibility of request_end(). Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
| * fuse: style fixesMiklos Szeredi2008-11-261-2/+2
| | | | | | | | | | | | | | Fix coding style errors reported by checkpatch and others. Uptdate copyright date to 2008. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* | fs: symlink write_begin allocation context fixNick Piggin2009-01-041-2/+2
|/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | With the write_begin/write_end aops, page_symlink was broken because it could no longer pass a GFP_NOFS type mask into the point where the allocations happened. They are done in write_begin, which would always assume that the filesystem can be entered from reclaim. This bug could cause filesystem deadlocks. The funny thing with having a gfp_t mask there is that it doesn't really allow the caller to arbitrarily tinker with the context in which it can be called. It couldn't ever be GFP_ATOMIC, for example, because it needs to take the page lock. The only thing any callers care about is __GFP_FS anyway, so turn that into a single flag. Add a new flag for write_begin, AOP_FLAG_NOFS. Filesystems can now act on this flag in their write_begin function. Change __grab_cache_page to accept a nofs argument as well, to honour that flag (while we're there, change the name to grab_cache_page_write_begin which is more instructive and does away with random leading underscores). This is really a more flexible way to go in the end anyway -- if a filesystem happens to want any extra allocations aside from the pagecache ones in ints write_begin function, it may now use GFP_KERNEL (rather than GFP_NOFS) for common case allocations (eg. ocfs2_alloc_write_ctxt, for a random example). [kosaki.motohiro@jp.fujitsu.com: fix ubifs] [kosaki.motohiro@jp.fujitsu.com: fix fuse] Signed-off-by: Nick Piggin <npiggin@suse.de> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: <stable@kernel.org> [2.6.28.x] Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> [ Cleaned up the calling convention: just pass in the AOP flags untouched to the grab_cache_page_write_begin() function. That just simplifies everybody, and may even allow future expansion of the logic. - Linus ] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fuse: implement nonseekable openTejun Heo2008-10-161-0/+2
| | | | | | | | Let the client request nonseekable open using FOPEN_NONSEEKABLE and call nonseekable_open() on the file if requested. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: fix SEEK_END incorrectnessMiklos Szeredi2008-10-161-0/+3
| | | | | | | Update file size before using it in lseek(..., SEEK_END). Reported-by: Amnon Shiloh <u3557@miso.sublimeip.com> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* [patch 3/5] vfs: change remove_suid() to file_remove_suid()Miklos Szeredi2008-07-261-1/+1
| | | | | | | | | All calls to remove_suid() are made with a file pointer, because (similarly to file_update_time) it is called when the file is written. Clean up callers by passing in a file instead of a dentry. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* fuse: lockd supportMiklos Szeredi2008-07-251-2/+9
| | | | | | | | | | | | | | | | | If fuse filesystem doesn't define it's own lock operations, then allow the lock manager to work with fuse. Adding lockd support for remote locking is also possible, but more rarely used, so leave it till later. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Cc: "J. Bruce Fields" <bfields@fieldses.org> Cc: Trond Myklebust <trond.myklebust@fys.uio.no> Cc: Matthew Wilcox <matthew@wil.cx> Cc: David Teigland <teigland@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fuse: add flag to turn on big writesMiklos Szeredi2008-05-131-0/+2
| | | | | | | | | | | | | | | | | Prior to 2.6.26 fuse only supported single page write requests. In theory all fuse filesystem should be able support bigger than 4k writes, as there's nothing in the API to prevent it. Unfortunately there's a known case in NTFS-3G where big writes cause filesystem corruption. There could also be other filesystems, where the lack of testing with big write requests would result in bugs. To prevent such problems on a kernel upgrade, disable big writes by default, but let filesystems set a flag to turn it on. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Cc: Szabolcs Szakacsits <szaka@ntfs-3g.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fuse: use clamp() rather than nested min/maxHarvey Harrison2008-05-011-1/+1
| | | | | | | | | clamp() exists for this use. Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Cc: Miklos Szeredi <miklos@szeredi.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fuse: fix race in llseekMiklos Szeredi2008-04-301-2/+27
| | | | | | | | | | | | Fuse doesn't use i_mutex to protect setting i_size, and so generic_file_llseek() can be racy: it doesn't use i_size_read(). So do a fuse specific llseek method, which does use i_size_read(). [akpm@linux-foundation.org: make `retval' loff_t] Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fuse: fix max i/o size calculationMiklos Szeredi2008-04-301-3/+4
| | | | | | | | | | | | Fix a bug that Werner Baumann reported: fuse can send a bigger write request than the maximum specified. This only affected direct_io operation. In addition set a sane minimum for the max_read and max_write tunables, so I/O always makes some progress. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fuse: update file size on short readMiklos Szeredi2008-04-301-6/+46
| | | | | | | | | | | | | | If the READ request returned a short count, then either - cached size is incorrect - filesystem is buggy, as short reads are only allowed on EOF So assume that the size is wrong and refresh it, so that cached read() doesn't zero fill the missing chunk. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fuse: implement perform_writeNick Piggin2008-04-301-1/+193
| | | | | | | | | | | | | | | | | | | Introduce fuse_perform_write. With fusexmp (a passthrough filesystem), large (1MB) writes into a backing tmpfs filesystem are sped up by almost 4 times (256MB/s vs 71MB/s). [mszeredi@suse.cz]: - split into smaller functions - testing - duplicate generic_file_aio_write(), so that there's no need to add a new ->perform_write() a_op. Comment from hch. Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Cc: Christoph Hellwig <hch@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fuse: clean up setting i_size in writeMiklos Szeredi2008-04-301-13/+15
| | | | | | | | | Extract common code for setting i_size in write functions into a common helper. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fuse: support writable mmapMiklos Szeredi2008-04-301-16/+305
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Quoting Linus (3 years ago, FUSE inclusion discussions): "User-space filesystems are hard to get right. I'd claim that they are almost impossible, unless you limit them somehow (shared writable mappings are the nastiest part - if you don't have those, you can reasonably limit your problems by limiting the number of dirty pages you accept through normal "write()" calls)." Instead of attempting the impossible, I've just waited for the dirty page accounting infrastructure to materialize (thanks to Peter Zijlstra and others). This nicely solved the biggest problem: limiting the number of pages used for write caching. Some small details remained, however, which this largish patch attempts to address. It provides a page writeback implementation for fuse, which is completely safe against VM related deadlocks. Performance may not be very good for certain usage patterns, but generally it should be acceptable. It has been tested extensively with fsx-linux and bash-shared-mapping. Fuse page writeback design -------------------------- fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM. It copies the contents of the original page, and queues a WRITE request to the userspace filesystem using this temp page. The writeback is finished instantly from the MM's point of view: the page is removed from the radix trees, and the PageDirty and PageWriteback flags are cleared. For the duration of the actual write, the NR_WRITEBACK_TEMP counter is incremented. The per-bdi writeback count is not decremented until the actual write completes. On dirtying the page, fuse waits for a previous write to finish before proceeding. This makes sure, there can only be one temporary page used at a time for one cached page. This approach is wasteful in both memory and CPU bandwidth, so why is this complication needed? The basic problem is that there can be no guarantee about the time in which the userspace filesystem will complete a write. It may be buggy or even malicious, and fail to complete WRITE requests. We don't want unrelated parts of the system to grind to a halt in such cases. Also a filesystem may need additional resources (particularly memory) to complete a WRITE request. There's a great danger of a deadlock if that allocation may wait for the writepage to finish. Currently there are several cases where the kernel can block on page writeback: - allocation order is larger than PAGE_ALLOC_COSTLY_ORDER - page migration - throttle_vm_writeout (through NR_WRITEBACK) - sync(2) Of course in some cases (fsync, msync) we explicitly want to allow blocking. So for these cases new code has to be added to fuse, since the VM is not tracking writeback pages for us any more. As an extra safetly measure, the maximum dirty ratio allocated to a single fuse filesystem is set to 1% by default. This way one (or several) buggy or malicious fuse filesystems cannot slow down the rest of the system by hogging dirty memory. With appropriate privileges, this limit can be raised through '/sys/class/bdi/<bdi>/max_ratio'. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fuse: save space in struct fuse_reqMiklos Szeredi2008-02-061-6/+8
| | | | | | | | | Move the fields 'dentry' and 'vfsmount' into the request specific union, since these are only used for the RELEASE request. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fuse: pass open flags to read and writeMiklos Szeredi2007-11-291-11/+15
| | | | | | | | | | | | Some open flags (O_APPEND, O_DIRECT) can be changed with fcntl(F_SETFL, ...) after open, but fuse currently only sends the flags to userspace in open. To make it possible to correcly handle changing flags, send the current value to userspace in each read and write. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fuse: fix reading past EOFMiklos Szeredi2007-11-291-1/+20
| | | | | | | | | | | | | | | Currently reading a fuse file will stop at cached i_size and return EOF, even though the file might have grown since the attributes were last updated. So detect if trying to read past EOF, and refresh the attributes before continuing with the read. Thanks to mpb for the report. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fuse_file_alloc(): fix NULL dereferencesAdrian Bunk2007-11-141-2/+3
| | | | | | | | | Fix obvious NULL dereferences spotted by the Coverity checker. Signed-off-by: Adrian Bunk <bunk@kernel.org> Acked-by: Miklos Szeredi <miklos@szeredi.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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