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NTFS: Fix a mount time deadlock.

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Big thanks go to Mathias Kolehmainen for reporting the bug, providing
debug output and testing the patches I sent him to get it working.

The fix was to stop calling ntfs_attr_set() at mount time as that causes
balance_dirty_pages_ratelimited() to be called which on systems with
little memory actually tries to go and balance the dirty pages which tries
to take the s_umount semaphore but because we are still in fill_super()
across which the VFS holds s_umount for writing this results in a
deadlock.

We now do the dirty work by hand by submitting individual buffers.  This
has the annoying "feature" that mounting can take a few seconds if the
journal is large as we have clear it all.  One day someone should improve
on this by deferring the journal clearing to a helper kernel thread so it
can be done in the background but I don't have time for this at the moment
and the current solution works fine so I am leaving it like this for now.

Signed-off-by: Anton Altaparmakov <aia21@cantab.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Anton Altaparmakov
2007-10-12 09:37:15 +01:00
committed by Linus Torvalds
parent f26e51f67a
commit bfab36e816
9 changed files with 181 additions and 53 deletions
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22
fs/ntfs/aops.c
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@ -2,7 +2,7 @@
* aops.c - NTFS kernel address space operations and page cache handling.
* Part of the Linux-NTFS project.
*
* Copyright (c) 2001-2006 Anton Altaparmakov
* Copyright (c) 2001-2007 Anton Altaparmakov
* Copyright (c) 2002 Richard Russon
*
* This program/include file is free software; you can redistribute it and/or
@ -396,7 +396,7 @@ static int ntfs_readpage(struct file *file, struct page *page)
loff_t i_size;
struct inode *vi;
ntfs_inode *ni, *base_ni;
u8 *kaddr;
u8 *addr;
ntfs_attr_search_ctx *ctx;
MFT_RECORD *mrec;
unsigned long flags;
@ -491,15 +491,15 @@ retry_readpage:
/* Race with shrinking truncate. */
attr_len = i_size;
}
kaddr = kmap_atomic(page, KM_USER0);
addr = kmap_atomic(page, KM_USER0);
/* Copy the data to the page. */
memcpy(kaddr, (u8*)ctx->attr +
memcpy(addr, (u8*)ctx->attr +
le16_to_cpu(ctx->attr->data.resident.value_offset),
attr_len);
/* Zero the remainder of the page. */
memset(kaddr + attr_len, 0, PAGE_CACHE_SIZE - attr_len);
memset(addr + attr_len, 0, PAGE_CACHE_SIZE - attr_len);
flush_dcache_page(page);
kunmap_atomic(kaddr, KM_USER0);
kunmap_atomic(addr, KM_USER0);
put_unm_err_out:
ntfs_attr_put_search_ctx(ctx);
unm_err_out:
@ -1344,7 +1344,7 @@ static int ntfs_writepage(struct page *page, struct writeback_control *wbc)
loff_t i_size;
struct inode *vi = page->mapping->host;
ntfs_inode *base_ni = NULL, *ni = NTFS_I(vi);
char *kaddr;
char *addr;
ntfs_attr_search_ctx *ctx = NULL;
MFT_RECORD *m = NULL;
u32 attr_len;
@ -1484,14 +1484,14 @@ retry_writepage:
/* Shrinking cannot fail. */
BUG_ON(err);
}
kaddr = kmap_atomic(page, KM_USER0);
addr = kmap_atomic(page, KM_USER0);
/* Copy the data from the page to the mft record. */
memcpy((u8*)ctx->attr +
le16_to_cpu(ctx->attr->data.resident.value_offset),
kaddr, attr_len);
addr, attr_len);
/* Zero out of bounds area in the page cache page. */
memset(kaddr + attr_len, 0, PAGE_CACHE_SIZE - attr_len);
kunmap_atomic(kaddr, KM_USER0);
memset(addr + attr_len, 0, PAGE_CACHE_SIZE - attr_len);
kunmap_atomic(addr, KM_USER0);
flush_dcache_page(page);
flush_dcache_mft_record_page(ctx->ntfs_ino);
/* We are done with the page. */