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    SubjectRe: [PATCH 2.4] FAT: do not continue in fat_get_block if bmap fails
    Hi Willy,

    On Tue, 2 Feb 2010 23:06:31 +0100
    Willy Tarreau <w@1wt.eu> wrote:

    > Hello Stefan,
    >
    > On Tue, Feb 02, 2010 at 02:00:35PM +0100, Stefan Seyfried wrote:
    > > From: Stefan Seyfried <seife@sphairon.com>
    > >
    > > There is no use in continuing the write operation after fat_bmap() fails.
    > > (This successfully killed a VFAT FS for me).
    > > The corresponding code in 2.6 does return here as well, AFAICT.
    >
    > OK then that's fine, I'm merging it.

    I'd like to add that I am not a filesystem expert at all, so if
    somebody wants to suggest a better return code, I'm all for that.

    And the dosfs code in 2.6 is substantially different, thus the "AFAICT"
    above ;)

    Anyway, continuing at that place (when phys == 0) is definitely
    wrong, since writing to block 0 later on will kill the filesystem 100%.

    I triggered this with a corrumpted file, which an application wanted to
    modify, dosfsck had this to say about the file system:

    strolchi:~ # dosfsck -nv /dev/sdb1
    dosfsck 2.11 (12 Mar 2005)
    dosfsck 2.11, 12 Mar 2005, FAT32, LFN
    Checking we can access the last sector of the filesystem
    Boot sector contents:
    System ID "MSDOS5.0"
    Media byte 0xf8 (hard disk)
    512 bytes per logical sector
    16384 bytes per cluster
    1 reserved sector
    First FAT starts at byte 512 (sector 1)
    2 FATs, 16 bit entries
    124928 bytes per FAT (= 244 sectors)
    Root directory starts at byte 250368 (sector 489)
    512 root directory entries
    Data area starts at byte 266752 (sector 521)
    62283 data clusters (1020444672 bytes)
    63 sectors/track, 32 heads
    247 hidden sectors
    1993577 sectors total
    /test/test.db
    File size is 188928 bytes, cluster chain length is 163840 bytes.
    Truncating file to 163840 bytes.
    Checking for unused clusters.
    Reclaimed 2 unused clusters (32768 bytes).
    Leaving file system unchanged.
    /dev/sdb1: 201 files, 51608/62283 clusters

    Thanks for merging and taking care of the "old lady" 2.4 ;)

    Stefan
    --
    Stefan Seyfried

    "Any ideas, John?"
    "Well, surrounding them's out."


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