]> pilppa.com Git - linux-2.6-omap-h63xx.git/commit
[PATCH] generic_file_buffered_write(): deadlock on vectored write
authorVladimir V. Saveliev <vs@namesys.com>
Tue, 27 Jun 2006 09:53:57 +0000 (02:53 -0700)
committerLinus Torvalds <torvalds@g5.osdl.org>
Wed, 28 Jun 2006 00:32:39 +0000 (17:32 -0700)
commit6527c2bdf1f833cc18e8f42bd97973d583e4aa83
tree737055ae276cdfa75e7b3e55a3ebdd1f88105606
parent1c0f16e5cdff59f3b132a1b0c0d44a941f8813d2
[PATCH] generic_file_buffered_write(): deadlock on vectored write

generic_file_buffered_write() prefaults in user pages in order to avoid
deadlock on copying from the same page as write goes to.

However, it looks like there is a problem when write is vectored:
fault_in_pages_readable brings in current segment or its part (maxlen).
OTOH, filemap_copy_from_user_iovec is called to copy number of bytes
(bytes) which may exceed current segment, so filemap_copy_from_user_iovec
switches to the next segment which is not brought in yet.  Pagefault is
generated.  That causes the deadlock if pagefault is for the same page
write goes to: page being written is locked and not uptodate, pagefault
will deadlock trying to lock locked page.

[akpm@osdl.org: somewhat rewritten]
Cc: Neil Brown <neilb@suse.de>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
mm/filemap.c