From: Andrey Savochkin <saw@saw.sw.com.sg>
To: Andrew Morton <akpm@osdl.org>
Cc: linux-kernel@vger.kernel.org
Subject: EXT3: problem with copy_from_user inside a transaction
Date: Fri, 3 Sep 2004 15:05:21 +0400 [thread overview]
Message-ID: <20040903150521.B1834@castle.nmd.msu.ru> (raw)
Hi Andrew,
filemap_copy_from_user() between prepare_write() and commit_write()
appears to be a problem for ext3.
prepare_write() starts a transaction, and if filemap_copy_from_user() causes
a page fault, we'll have
- order violation with mmap_sem taken inside a transaction (possible
deadlocks),
- __GFP_FS memory allocation with all re-entrancy problems (e.g.,
current->journal_info corruption).
Am I missing something?
If this observation is correct, the possible solution is to call
get_user_pages() or somehow pin the user pages before prepare_write(),
although it will hurt performance...
Andrey
next reply other threads:[~2004-09-03 11:05 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-03 11:05 Andrey Savochkin [this message]
2004-09-03 12:35 ` EXT3: problem with copy_from_user inside a transaction Andrea Arcangeli
2004-09-03 12:06 ` Chris Mason
2004-09-03 13:03 ` Andrea Arcangeli
2004-09-03 13:57 ` Andrey Savochkin
2004-09-04 7:47 ` Chris Mason
2004-09-04 14:33 ` Andrey Savochkin
2004-09-04 20:12 ` Andrey Savochkin
2004-09-07 11:55 ` [RFC][PATCH] " Andrey Savochkin
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